Patent GB-558781-A (GB)
Title: Improvements in or relating to automatic telegraph exchange systems
IPC: H04L12/54
Filed: 1942-05-29
Abstract: 558,781. Teleprinter exchange systems. STANDARD TELEPHONES & CABLES, Ltd. May 29, 1942, No. 7306. Convention date, May 31, 1941. [Class 40 (iii)] Relates to automatic teleprinter exchange systems having facilities for the multiple transmission of the same message simultaneously to two or more lines. The messages are recorded at the exchange, e.g. in perforated tape, so that, if a wanted line is busy, the message may be transmitted to it when it becomes free. The message may be transmitted simultaneously to those lines which are free or in succession as the lines become free. If a number of messages accumulate for any line, an operator at the exchange may cause a waiting message to be rerecorded at an overflow position for subsequent transmission when the line becomes free. A calling party sending an urgent message may transmit a special code combination for the letter U (before any other code signals) to attract the attention of the exchange operator who may take steps to handle the recorded urgent message out of turn. The invention is described as applied to a system having two exchanges connected by a two-way trunk. The system has only a few subscribers, these being designated by a single letter, so that a caller selects the desired line by sending the permutation code signal of that letter. Certain letters such as M, U, X are reserved for special calls, M for calls to several lines at once, U for urgent calls, and so on. Each call is prefixed by the " figures " and H codes, a combination of codes which cannot occur in succession in ordinary messages. These codes are also transmitted at the end of a message, and serve to condition the apparatus for operation. A normal call therefore comprises the " figures code, the H code, a letter code, say B, corresponding to the designation of the wanted line, the message in code, and finally the " figures" and H codes again. The system described is not suitable for detailed abridgment but a general idea of its operation may be obtain from the following description of the equipment and circuits at one exchange, and from the description of the way in which a message is conveyed from one subscriber to another on the same exchange. Fig. 3 shows one exchange having (1) connections to two subscribers A, B, (2) a two-way trunk 226 leading to a similar exchange, (3) a circuit 352 leading to a manual or other switching station C, (4) an operator's transmitter 362 by which an operator may send a message to any subscriber or to the other exchange, and (5) equipment 372, 374 accessible to any line for transmitting the same message to several lines. Each subscriber's line A, B and the two-way trunk 226 terminates at the exchange in a teleprinter 311, 331, 321 to record messages for the exchange, and in a printer-perforator 312, 332, 322 to print and perforate messages intended for other stations reached through the exchange. The circuit 352 leading to station C similarly terminates in a teleprinter 341 and printer-perforator 342 for messages from station C, and is also associated with a printer-perforator 347 and transmitter 346 by which messages from other stations may be sent to station C. Tape punched by the perforator 312, 322, 332, 342, 362, or 372 passes to the automatic transmitter and associated distributer 314, 324 &c. from which controlling, switching and message signals are transmitted. The controlling and switching signals control the switching relays shown on the right of Fig. 3 to extend the call to the desired line or exchange position. Construction of transmitter such as 314, 324, &c. The tape 500, Fig. 6, perforated in a printerperforator, such as 312, Fig. 3, is engaged by five pins 663 controlling contacts 681 connected to the segments of distributer 673. The pins 663 are associated with five notched bars 667 cooperating with cross-bars 664 controlling contacts 621, 622 &c. These contacts when closed by the control and switching code signals preceding the message signals, control switching and selecting operations whereby the message signals are directed to the desired line or circuit. A contact 682 is closed when the tape is taut. A magnet 671, when energized, disconnects the normal ratchet tape feed. Construction of combined printer-perforator.- selector, such as 312, 322, &c.-The code bars 2518, Fig. 25, are set by the selecting-magnet 2548 in known manner and select the desired type-bar 2501 to print the selected character. The five code bars 2518 are connected through linkage levers 2520, 2521, 2529 and 2522 to interponents 2523 controlling the perforation of the tape in the usual manner. Certain of the type-bars 2501 control contacts, such as 2538, which have a controlling or selecting function as described later. Transmission of message from station A, Fig. 5, to the exchange for subsequent transmission to station B.-Fig. 5 shows station A connected by line 589 to a printer-perforator and teleprinter at the exchange, the punched tape 500 passing to the transmitter shown in Fig. 6. Normally current passes from battery at the exchange over line 589, substation A, line 589, relays 547, 592 and lead 550. As previously stated, subscriber A transmits in succession " figures," H, B (to select station B), and then message signals. The " figures" signals are repeated by relay 547 to a slow-release relay 560 and to magnet 548 which operates the code bars to close a contact to energize relay 561 which locks. The H signals similarly close a contact to energize relay 562 which locks. (The "figures" and H signals are also repeated by relay 592 to the magnet 593 of the teleprinter but without effect since this magnet is permanently connected to battery by relay 565 at this time.) Relay 560 energizes a relay, which lights a busy lamp and prevents connections being made to line A by other subscribers. The " figures and H signals are also printed and punched in the tape 500. The B signals are then punched in tape 500 and open contacts 533 to de-energize relay 562. The message signals, followed by the " figures and H signals, are similarly recorded in the tape 500. The "figures" and H signals at the end of the message energize the relays 561, 562 as before, relay 562 opening a circuit so that the station A can receive calls from other lines. Transmission of the message to the selected station.-Where a message is recorded in the tape 500, this becomes slack, closing contact 682, Fig. 6, thereby energizing relay 650 which closes the circuit of the start-stop magnet 672 of the distributer which is released to transmit the signals recorded in the tape. No significant effect is produced until the "figures" signal is reached. This closes contact 618 energizing relay 707 which locks up. The next signal H closes contact 617 energizing relay 706 which locks up. The next signal B closes contact 613 energizing relay 702, which locks up dependent on relay 708 and opens the locking circuit of 706. Relay 202 (1) closes a circuit for magnet 671 which prevents feed of the tape until the transmission circuit has been extended to line B, (2) opens the circuit of the start-stop magnet 672 to arrest the distributer, (3) energizes relay 837 individual to line B. If line B is busy, relay 830 is energized and lamp 863 lit. If line B is free or when it becomes free, relay 837 energizes relay 838, which (1) locks up over its left-hand winding, (2) energizes relay 830 to mark line B busy and light lamp 863, (3) energizes relay 839, and (4) completes the transmission circuit to line B from battery, permutation contacts 681, distributer 673, lead 645 through Fig. 7 to contacts of relay 838, and thence through a circuit not shown including the contacts of switching relays in Figs. 11, 18, 21, 24, 21, 18, 14, 13 (not shown) to lead 1268, Fig. 12, relays 1292, 1247 over the line 1289 to subscriber B and back over the line to battery at the exchange. Relay 839 which, like relays 837, 838, is individual to lines A and B, completes a circuit (not fully shown) over lead 1259 for relay 1265, Fig. 12, which (a) locks up over a circuit including contact 1291, (b) disconnects positive battery from magnet 1293 of the teleprinter so that will respond to the impulses passing through relay 1292 and make an exchange copy of the message sent to line B, (c) connects positive battery to the magnet 1248 of the printer-perforator so that this will not respond to the impulses passing through relay 1247 to line B. Relay 839 also open-circuits relay 708 which opens the locking-circuit of relay 702, re-establishing the circuit of the start-stop magnet 672, thereby starting the distributer and automatic transmitter which sends the recorded message (including the letter B) over the transmission circuit described above. Operation when transmission of message is completed.-The final "figures" and H signals energize relays 707, 706 as before, relay 706 opening part of the locking circuit of relay 838 which de-energizes when the other branch of the locking circuit is opened when the transmission of letter H is complete. The successive transmission of " figures " and H also opens contact 1291 in the teleprinter, thereby opening the locking circuit of relay 1265, which de-energizes as soon as the energizing circuit over lead 1259 is opened by relay 839 controlled by 838. The de-energization of relay 1265 restores the teleprinter and printer-perforator of line B to normal. Relay 838 also opens the circuit of relay 830 so that line B is free to receive calls. Operation when receiving station breaks-in.- If subscriber B depresses break key 1284 for a prolonged period, switch 1295 associated with teleprinter 1290 is operated to arrest the transmitter, Fig. 6, and light lamp 1296, and the operator can communicate with the subscriber and if necessary move back the tape 500 so that the entire message is again transmitted. Tape feed-out.-When the tape 500 becomes taut at the end of the